Throttle Body Coolant Bypass (with pics), Want to bypass the coolant flow to your Throttle Body on you 5SFE? Options

[Spider77]

So, after quite a few PM's on how to do this I finally broke down and took some pics. You will notice however that I did not put everything back to "factory settings", ie, I just took a few pictures and hope that they'll help the ones who want to know how to do this.
First off though, a warning:
****THE COOLANT WILL BE HOT AFTER RUNNING THE ENGINE, THEREFORE TO AVOID BURNS I STRONGLY SUGGEST THAT YOU LET THE ENGINE/COOLANT SYSTEM COOL DOWN BEFORE ATTEMPTING TO DO THIS, I AM IN NO WAY RESPONSIBLE FOR PERSONAL HARM THAT MAY BE CAUSED WHILE ATTEMPTING THIS, YOU HAVE BEEN WARNED****

STEPS:
1:) You want to start by disconnecting your SRI/CAI/Stock Intake at the throttle body:

2:) Disconnect the 4 Vac lines (three on top, one that sits lower):

3:) Disconnect the Throttle Cables (one for Man, two for Auto):

4:) Remove TB by pulling the 4 12 mm bolts:

5:) Remove TB from Intake Plenum:

6:) You will notice three lines hooked into the TB, two outside line (coolant) and one middle line (vac). You want to "bypass" the TB by linking the two coolant lines together, using a 5/16th brass bard (male to male) fitting and screw clamps to tighten it down. Please do not use existing hardware as its probably been sitting there for a while and chances are it wont stand up. Please use new hardware (screw clamps).




7: After you insert brass barb (male to male fitting) and tighten down the screw clamps, you might want to install some vac caps on the coolant ports. Although I cant say if its required, for me its just piece of mind):

8: Reattach the Vac line (its the middle port)!

8.5: Totally optional, but at this time I did a minor cleaning of the TB, and the butterfly valve. Not required, but while its open, might as well, right?
9: Check your work. This is what you should have, two coolant lines "looped" together, two coolant ports capped (optional), and the Vac line (the middle port) reattached. Make sure that your screw clamps are tight (either use a socket or the right size four point to make sure its super tight...don't want leaks), and again, check another time. Once you are sure everything is done, place your throttle body back on the intake plenum, place the SRI/CAI/Stock Intake back on, and enjoy!

While I can not say this is how it is for different engines, the concept is the same. So, for all those people PM'ing me, this is how you do it (again ,mind you its not a pure step by step, but you'll get the idea), and for those who want to know how to TB Bypass on the 5SFE, here you go!
I hope this can help answer this question to some extent. If anyone sees anything wrong with this (ie mislabeling please let me know so I can correct).
Thanks and hope you enjoy!

[Robbie1902]

Very nice write up!

[mkernz22]

vote for sticky!

[4-eyed-freek]

sticky!

[hatchy_gt-s]

Not to sound like a dick but those are there for a reason, toyota wasn't like hey lets put 2 random @$$ coolant lines into the intake. They're there for proper idling when cold. Also removing them doesn't accomplish anything, the air you intake is moving to fast to be affected.

You can remove a lot of things off a stock motor(egr, thermostat, iac lines, exe.)without major problems, BUT it will cause problems down the road.

Now Im not telling you what to do but other people need to hear both sides of the story.

Very well put together How To:, good job spider77

This post has been edited by hatchy_gt-s: Oct 24, 2010 - 10:31 PM

[4-eyed-freek]

i just dont understand why toyota would run coolant throught the trottle body in the first place.. if it didnt have it, the heat from the engine is still heating it up.. and as for cold starts... hahah well the coolants going to be cold to. and if there worried about freezing, they shouldnt worry unless you dumped water into your intake in the middle of winter. i agree with hatchy gt-s, we should hear both sides, but how would this affect idle? and cold starts?

[Spider77]

Well, the one reason why I had it set up like this is because it is fairly easy to hook back up the way it was. Seriously, the hardest part about this is removing the TB from the intake plenum. As far as Idle problems, I have not experienced any yet.

[sphinxxx]

sorry for the newb question, but what is this for in the first place? i dont get it!

[4-eyed-freek]

coolant runs through your throttle body making it very warm.. the down side to any engine it taking in warm air, you car wants the air it takes in to be as cold as posible, so bypassing the throttle body helps with taking away that warm water going around it.

sorry for the newb question, but what is this for in the first place? i dont get it!

[fgvillegas]

i was thinking if the effects of doing this will be negated if you have an alluminum intake pipe. because as your engine gets hotter, the intake pipe will get hotter too and this could heat up the air coming in. although, i'm not sure which is hotter. but the thing is, the area that the coolant heats up is much smaller that the intake pipe specially if you have a CAI setup.

what do you think?

[Akirad1]

i have to agree with spider77 since we live in Texas and it doesn't get to cold during our winters, so there is no point to have our intakes heated up and like what he said if it does get cold enough to need it is just a matter of hooking it back up. But for our hot as hell Texas summers we don't need our intakes warmed up.

[Tom_SS2]

it's not meant to heat the intake as such it's to prevent the throttle freezing/sticking open when really cold afiak

[Langing]

i have to agree with spider77 since we live in Texas and it doesn't get to cold during our winters, so there is no point to have our intakes heated up and like what he said if it does get cold enough to need it is just a matter of hooking it back up. But for our hot as hell Texas summers we don't need our intakes warmed up.

Stumbled upon a relevant patent, priority date July 12, 2000, that showed three coolant 'bypass' passages, relatively independent water channels that lead from the back of an engine to the front (water pump), inside of (bypassing) the coolant pathways to and from the radiator. It showed no thermostat, as it uses a computer controlled FLOW CONTROL VALVE to switch from full flow through the TB when the engine is cold, to no flow through the TB when the engine is hot (the situation that spider77 creates. . . permanently).

One of the passages was just a pipe from the back to the front (called RESTRICTION in the patent).

One passage went from the back of the engine through the heater and then back to the pipe leading to the front.

The third passage went through the Exhaust Gas Recirculation (EGR) valve , then through the throttle body (TB), then to the FLOW CONTROL VALVE, and then back to the pipe leading to the front.

You can imagine them as three parallel 'bypass' coolant passages, at least at the point where hot water comes out of the operating engine. They don't all carry coolant all the time (e.g., the heater only carries coolant when you turn your heater on). But they can (e.g., the passage through the EGR valve and TB), unless the computer instructs it to slow or close.

A fourth passage in the patent was the main one, the passage that goes out to your radiator and then back into the engine.

The patent showed the EGR/TB passage and the Radiator passage coming together at a FLOW CONTROL VALVE, so the computer would have the ability to control how much coolant moved through the TB. Evidently, this newer design would allow the computer to completely cut off the flow through the TB once the engine reaches its normal operating temperature.

The main claim of this patent was that by control of the flow through the TB they were able to cut the warm-up time of the engine from something like 250 seconds to something like 187 seconds.

Not being privy to the design decisions that Toyota used to set up any of its engines, I took this to be the reason that they piped coolant through the throttle body. It's a way to significantly decrease the time it takes to get the engine from ambient temp up to normal operating temperature. Every time you start your engine, you have to go through this 'warm up' period, even if you live in the hottest part of Texas. The operating temp of an internal combustion engine certainly must be much hotter than that.

I believe the overall engine design depends on operating temperature to a great extent, so getting to that point quicker, in an ordinary car, has benefits that none of us has the background to truly appreciate.

Now, on our older vehicles, on the other side of the issue we have 'shorted out' one water cooled/heated element (TB), intending on preventing a hot TB from heating up the intake air, which only matters when the engine has reached its normal operating temperature, which we have time delayed. Someone above suggested that the airflow through the throttle body was so rapid that a hot TB would not make much of a contribution toward heating the intake air. I'm not sure that's the total answer, but can offer a bit more information.

The Exhaust Gas Recirculation (EGR) system is part of your engine's emissions control. It's main function is to reduce or eliminate the generation of NOX (exhaust gasses containing oxides of nitrogen), since NOX causes smog and acid rain. NOX is created when the fuel burn occurs in a cylinder that is above a certain temperature, a temperature that would normally be reached under normal conditions, so, under certain engine operating conditions (load, temp, etc) the computer intentionally reduces the combustion temperature by adding a small amount of exhaust gas (NOTE: inert gas) which has the overall effect of lowering combustion temperature (which lowers your useful hp, and mileage, of course ).

There is a pipe that routes exhaust gas directly from the exhaust manifold back to the EGR valve, which controls the amount that is added back to the intake air. I'm guessing that HOT exhaust air moving into the intake air flow must have a much larger effect than what heat could be transferred by the hot coolant continuously running through the TB. But, then again, the EGR doesn't turn on all the time. It's off at idle. It comes on only when the engine temp reaches a certain value, and even then when there is significant load on the engine. So, it's hard to know for certain what is best for your engine.

The only reason I know this stuff is because I just finished troubleshooting and fixing a CHECK ENGINE LIGHT (MIL) that came on due to a 'excess EGR flow' code P0204 (?) on my 2000 Tacoma. Found a bad Vacuum Switching Valve (VSV). While at it, I took apart everything up to the intake plenum to clean out all the carbon, varnish and whatnot out of my TB. When I went to put it all back together I ran across those stupid water hoses and had a devil of a time figuring out how to connect it all back up properly. That made me search and read a whole lot about the subject at hand, and during that exercise I ran into videos on YouTube that showed exactly what Spider77 shows you how to do at the top of this thread (and Spider77 did it so well he should be much appreciated).

Yet, I wondered deeply why someone would do that, and concluded that it would definitely be a help if one had a race car engine that doesn't have emissions controls on it. Because then every minute contribution of heat going into the engine air intake would need to be eliminated. Other than that, I really don't see the true benefit (it's got to be a trade-off), and I worry that there is a detriment to the long term operation of your engine due to extended lengths of warm up times.

[doory100]

Main question is there any gain in doing this?

[Bitter]

Nothing that can be measured reliably.

[Langing]

Main question is there any gain in doing this?

And the flip side. . . is there any loss?

Bitter probably has the right answer to both questions. My opinion: it is worse to shunt (bypass) the TB because it would shorten the life of the engine (by some unmeasurable amount, Bitter would correctly add).

[Bitter]

It's there to prevent icing of the throttle plate and IAC under certain driving conditions, like high humidity and medium to lower ambient temps. The pressure drop across a small opening like the throttle plate can cause the air to be cold enough to condense the water out and freeze it. Ice in your throttle is bad, in the IAC it stops it from being able to idle the car right or at all. Typically the heat conducted through the metal intake manifold would be enough, but if you've just started driving and the intake manifold is cold there's a potential for icing. The hottest coolant available is routed for the throttle, so it warms up fast and prevents icing. The amount of surface area in the throttle body, the speed at which air passes through, and the time which it has to absorb heat through contact (not to mention the insulating effects of the boundary layer) mean that very very very little heat is gained there. You'll pick up more heat from the intake manifold and cylinder head port than the throttle body I would think. It's one of those 'I did this thing and spent time on it and it cost me nothing so yes it definitely did something', though I really doubt it does.

Do it, don't do it, odds are there's no gain and very little chance you'll ice the throttle body. Just remember though, auto makers are the ultimate penny pinchers and they always heat the throttle body, they must have some reason.

[VavAlephVav]

I examined the Idle Speed Control Valve when I had my throttle-body off and was trying to get it to idle right.
On the back side of the ISCV is the cover plate with two small screws, and it is slightly adjustable. I meant to take some pics of this while I had it off but ran out of time.
inside there is a slot-n-groove contraption that holds a Bi-metal spring in place. now, the idle speed is controlled by turning the little valve inside to adjust the exact amount of air allowed into the intake when the throttle plate is closed(idling).
on the front side is the magnetic coil which the computer uses to control the position of the idle valve, on the back side of the rod that controls the idle valve is this Bi-metal spring.
a bi-metal spring is simply a device made of two different metals, maybe steel and brass or something, and as they get hot the two metals expand at different rates and cause the coiled spring to expand in a particular way that moves the idle air valve.

so it seems to supplement the control of the idle valve in some way, although im not yet sure how. The coolant lines run though passages that effect the temperature of this bi-metal spring. I am guessing that as the engine coolant warms up the bi-metal spring
expands and this mechanically moves the idle valve in the direction that closes is slightly more than it was, lowering the idle speed as it warms up.
the question is, why doesn't the computer just use the temp readings from the Coolant Temperature Sensor and adjust the idle speed accordingly??

however I'm not really sure that this is all there is to the way this system works. It's just what I guess.
maybe the general idle speed is controlled by the computer and this bi-metal spring just drops the idle a bit as the engine warms up.
This would mean a couple of things: 1. adjusting the exact position of that little plate will effect your idle speed. 2. doing the mod of this OP will cause your engine to idle too high.

[VavAlephVav]

7: After you insert brass barb (male to male fitting) and tighten down the screw clamps, you might want to install some vac caps on the coolant ports. Although I cant say if its required, for me its just piece of mind):

these two pics show the back side of the ISCV and cover plate I'm talking about. under this is the bi-metal spring.
see it is adjustable.

I am most certain that the coolant runs though there Just to effect that bi-metal spring (it's more of a coil shape like inside of a cheap house thermostat)



This post has been edited by VavAlephVav: Sep 9, 2014 - 10:12 PM

[Bitter]

It may just be a coil spring to make sure the IAC fails fully open when it fails? Maybe it is a bi-metal spring and it's a backup in case it fails electrically? Someone should take one apart and find out, I'd be interested to know.